The present invention relates generally to fuel systems, and more specifically to a method of priming fuel systems using an electronic control system.
It is known in the art that when an engine is shut down and allowed to remain inactive for a period of time, fuel pressure within the engine""s fuel system will decay. In addition, when the engine has remained inactive for a relatively long period or when the engine is shut down hot and allowed to cool to ambient air temperature on a cold day, the fuel will contract allowing vapor and/or air bubbles to form within the fuel system. Further, when the fuel system is drained for maintenance purposes, the fuel within the system must be replaced. Thus, in order to re-start the engine, the fuel system must be primed with fuel, and the pressure within the fuel system must be raised.
In many fuel systems, the pressure within the fuel system is raised by a high pressure pump. A fuel transfer pump supplies the fuel to the high pressure pump, and the high pressure pump pressurizes the fuel and delivers it to a common rail. It is known in the art that, in order to effectively operate the high pressure pump, the fuel flowing from the fuel transfer pump into the high pressure pump must be at a threshold inlet pressure. Once the fuel enters the high pressure pump, the high pressure pump must further raise the pressure of the fuel to an outlet valve opening pressure in order to permit the flow of fuel from the high pressure pump to the common rail. The high pressure pump can then prime the common rail with fuel and raise the pressure of the common rail to injection pressures.
Often, the high pressure pump and the fuel transfer pump are operably coupled to the engine. Thus, once engine cranking has begun, it takes time for the fuel transfer pump to raise the pressure of the fuel being supplied to the high pressure pump to the threshold inlet pressure. Moreover, once engine cranking has begun, it takes time for the high pressure pump to create pressure sufficient to open the outlet valve of the high pressure pump. Because the priming of the common rail is dependent on the output of the high pressure pump which in return is dependent on the output of the fuel transfer pump, the engine crank time is increased by the high pressure pump and the fuel transfer pump.
Over the years, engineers have developed various strategies for priming a fuel system and reducing engine cranking time. One such strategy is the use of electrically powered priming pumps. For instance, the fuel system shown in U.S. Pat. No. 5,878,718, issued to Rembold et al., on Mar. 9, 1999, includes an electrically powered fuel transfer pump that also acts as the priming pump. Upon initiation of the engine, the Rembold pump is electrically activated and begins supplying fuel to a mechanical high pressure pump and fuel common rail. However, if pressure sensors sense that the fuel system is in an unprimed state, an electronically controlled valve will be activated in order to increase the delivery of the fuel transfer pump. The fuel transfer pump will then act as the priming pump and deliver fuel to the common rail via a fuel connection line that bypasses the high pressure pump that is operably coupled to the engine. By bypassing the high pressure pump, fuel can be delivered to the common rail without being hindered by the high pressure pump. When the high pressure pump is fully activated and is supplying high pressure fuel to the common rail, the electronically controlled valve is returned to its normal engine operating position, reducing the delivery from the electrically powered pump. The electrically powered pump will act as the fuel transfer pump and deliver fuel to the common rail via the high pressure pump, rather than by bypassing the high pressure pump.
Although the Rembold pump illustrates one strategy for reducing engine crank time and priming the fuel system, there is room for improvement. For instance, in larger engines, such as those used in conjunction with generators, marine applications, and locomotives, it is often inefficient and impractical to use an electrically-powered fuel transfer pump. The larger the engine, the larger the fuel transfer pump, and thus, the more energy required to operate the fuel transfer pump. Often, hand priming pumps or manually activated priming pumps are used. Further, for engines with specific applications, such as engines used with generators in case of emergencies, the system should be able to prime the common rail prior to initiation of the engine start-up in order to assure relatively quick engine starts. For instance, in a hospital where the primary power source is interrupted, the engine used in conjunction with the generator must be able to start operating and providing mechanical energy to the generator within a specified short period in order to maintain the operation of the hospital""s equipment and to meet federal regulations. The Rembold pump that is not activated until initiation of the engine start cannot assure a primed common rail in an inactive engine.
The present invention is directed to overcoming one or more of the problems set forth above.
In one aspect of the present invention, a fuel system includes a first fuel pump that is electrically powered and in communication with an electronic control module. A second fuel pump is operably coupled to an engine. The electronic control module includes a priming algorithm that is operable to activate the first fuel pump when the fuel system is in an unprimed state.
In another aspect of the present invention, a control system includes an electronic control module in communication with at least one sensor operable to sense a state of the fuel system. The electronic control module includes a priming algorithm that is operable to activate an electrically powered fuel pump when the state of the fuel system is unprimed.
In yet another aspect of the present invention, a fuel system is primed by first determining whether the fuel system is in an unprimed state. If the fuel system is in an unprimed state, an electrically powered pump is activated via an electronic control module.